Altermagnetic materials, especially ${\mathrm{RuO}}_2$, have recently attracted considerable attention for their unique magnetic properties and energy-efficient spintronic applications. However, recent experimental studies have reported highly conflicting signatures regarding altermagnetic spin splitting and charge-spin interconversion (CSI) in ${\mathrm{RuO}}_2$. While some experiments link efficient CSI to nonrelativistic altermagnetic spin-splitting effects, others observe large CSI signals in non-spin-splitting ${\mathrm{RuO}}_2$, which are instead explained by relativistic inverse spin Hall effects. In this Letter, based on first-principles calculations, we reveal that these controversial experimental results originate from a phase-dependent coexistence and relative dominance of the orbital Hall effect (OHE) and spin Hall effect (SHE) in ${\mathrm{RuO}}_2$. We systematically investigate the OHE and SHE in both altermagnetic and nonmagnetic phases of ${\mathrm{RuO}}_2$. Our results show that the altermagnetic state hosts a giant OHE that exceeds the SHE by 2 orders of magnitude and carries an opposite sign. This dominant OHE can generate experimentally observed “SHE-like” voltages through orbital-to-spin conversion, explaining previously reported altermagnetic CSI signals. In contrast, OHE of nonmagnetic ${\mathrm{RuO}}_2$ is suppressed and a large relativistic SHE emerges, in agreement with recent angle-resolved photoemission and spin-pumping experiments. Finally, we demonstrate that the coexistence of OHE and SHE is tunable via chemical doping, enabling on-demand modulation of CSI in ${\mathrm{RuO}}_2$. Our work provides a new physical mechanism for understanding CSI in ${\mathrm{RuO}}_2$ and highlights the central role of orbital transport.

Guiding electromagnetic waves far below the diffraction limit usually produce severe propagation loss because the field is forced into dissipative material boundaries. We discover that a metal-Epsilon-near-zero (ENZ) interface can support an optical antiskin effect, significantly reducing propagation loss by orders of magnitude while preserving subdiffraction confinement. In the proposed metal-ENZ-high-index-air (MEHA) line, a nanoscale ENZ shell suppresses the lossy surface-bound mode and pushes it above a dielectric-confined mode in the modal hierarchy, allowing the low-loss volume mode to serve as the fundamental guided state. Realistic $\mathrm{Ag}/\mathrm{GaAs}/\mathrm{Si}$ MEHA lines support a mode-reordered terahertz band with robust bend transmission. This boundary-engineering mechanism establishes a compact, bend-tolerant, low-loss metallic-waveguide platform for high-density terahertz and midinfrared integration and localized wave delivery.

Stretched exponential distributions of nonequilibrium steady-state fluctuations are ubiquitous in living and nonliving systems alike, yet their microscopic origins have remained elusive. In this Letter, we track the motion of three types of vesicles across different cell types and find that their trajectories undergo random transitions between directed runs (on state) and diffusionlike jiggling (off state) in the highly dynamic, heterogeneous cytoplasm. The dwell times in these two states follow a stretched exponential distribution, which arises from a continuous weighted sum of simple exponential distributions that align with the unbinding kinetics of motor proteins traversing the cytoskeletal filaments in vitro. Our findings illuminate the profound connection between stretched exponential statistics and dynamic heterogeneity, shedding new light on the complex spatiotemporal landscape of cargo transport within cells.

We argue that the presence of any exact U(1) higher-form symmetry, under mild assumptions, presents a fundamental obstruction to ergodicity under unitary dynamics in lattice systems with local interactions and finite on-site Hilbert space dimension. Focusing on the two-dimensional case, we show that such systems necessarily exhibit Hilbert space fragmentation and explicitly construct Krylov sectors whose number scales exponentially with system size. While these sectors cannot be distinguished by symmetry quantum numbers, we identify the emergent integrals of motion that characterize them. Our symmetry-based approach is insensitive to details of the Hamiltonian and the lattice, providing a systematic explanation for ergodicity breaking in a range of systems, including quantum link models.

The evolution of an isolated quantum system inevitably exhibits recurrence: the state returns to the vicinity of its initial condition after finite time. Despite its fundamental nature, a rigorous quantitative understanding of recurrence has been lacking. We establish upper bounds on the recurrence time, $t_{\mathrm{rec}}\lesssim t_{\mathrm{exit}}(\epsilon )(1/\epsilon {)}^d$, where $d$ is the Hilbert-space dimension, $\epsilon$ the neighborhood size, and $t_{\mathrm{exit}}(\epsilon )$ the escape time from this neighborhood. For pure states evolving under a Hamiltonian $H$, estimating $t_{\mathrm{exit}}$ is equivalent to an inverse quantum speed limit problem: finding upper bounds on the time a time-evolved state ${\psi }_t$ needs to depart from the $\epsilon$ vicinity of the initial state ${\psi }_0$. We provide a partial solution, showing that under mild assumptions $t_{\mathrm{exit}}(\epsilon )\approx \epsilon /\sqrt{\mathrm{\Delta }(H^2)}$, with $\mathrm{\Delta }(H^2)$ the Hamiltonian variance in ${\psi }_0$. We show that our upper bound on $t_{\mathrm{rec}}$ is generically saturated for random Hamiltonians. Finally, we analyze the impact of coherence of the initial state in the eigenbasis of $H$ on recurrence behavior.

The performance of quantum annealing for combinatorial optimization is fundamentally limited by the minimum energy gap $\mathrm{\Delta }$ encountered at quantum phase transitions. We investigate the scaling of $\mathrm{\Delta }$ with system size $N$ for two paradigmatic quantum spin-glass models: the two-dimensional Edwards-Anderson (2D-EA) and the all-to-all Sherrington-Kirkpatrick (SK) models. Utilizing a newly proposed unbiased energy-gap estimator for continuous-time projection quantum Monte Carlo simulations, complemented by high-performance sparse eigenvalue solvers, we characterize the gap distributions across disorder realizations. It is found that, in the 2D-EA case, the inverse-gap distribution develops a fat tail with infinite variance as $N$ increases. This indicates that the unfavorable superalgebraic scaling of $\mathrm{\Delta }$, recently reported for binary couplings [M. Bernaschi et al., The quantum transition of the two-dimensional Ising spin glass, Nature (London) 631, 749 (2024)], persists for the Gaussian disorder considered here, pointing to a universal feature of 2D spin glasses. Conversely, the SK model retains a finite-variance distribution, with the disorder-averaged gap following a rather slow power law, close to $\mathrm{\Delta }\propto N^{-1/3}$. This finding provides a promising outlook for the potential efficiency of quantum annealers for optimization problems with dense connectivity.

High-fidelity quantum gates are essential for scalable quantum computation. However, at short durations, short-timescale waveform distortions break the time-reflection symmetry of control pulses, preventing the precise closure of cyclic evolution. This mechanism renders conventional symmetric protocols intrinsically overconstrained. Conventional strategies typically rely on smoothing the pulse envelopes or embedding the interaction pulse within a longer qubit pulse to bypass short-timescale distortions, which inevitably leads to a persistent speed-fidelity trade-off. To overcome this limitation, we introduce a cyclic control strategy based on parameter-space expansion, which restores controllability by incorporating an additional degree of freedom. We experimentally demonstrate this approach in a superconducting controlled-z gate, achieving robust suppression of coherent errors without increasing gate duration, reducing the average coherent error from 0.27% to 0.12% across multiple two-qubit gates, as validated by cross-entropy benchmarking. Our results establish a general route to fast, high-fidelity cyclic quantum gates beyond the conventional speed-fidelity trade-off.

Bosonic codes constitute a promising route to fault-tolerant quantum computing. Existing Floquet protocols enable analytical construction of bosonic codes but typically rely on slow adiabatic ramps with thousands of driving periods. In this Letter, we circumvent this bottleneck by introducing an analytical and deterministic Floquet method that directly synthesizes arbitrary unitaries within a single period. The phase-space unitary ensembles generated by our approach reproduce the Haar-random statistics, enabling practical pseudorandom states in continuous-variable systems. We prepare various prototypical bosonic codes from vacuum and implement single-qubit logical gates with high fidelities using quantum lattice gates. By harnessing the full intrinsic nonlinearity of Josephson junctions, quantum lattice gates decompose quantum circuits into primitive operations for efficient continuous-variable quantum computing.

We implement a decoy-state quantum key distribution scheme using a telecom C-band single-emitter source. The decoy states are created by varying the optical excitation of the quantum emitter to modulate the photon-number distribution. We provide an analysis of our scheme based on existing security proofs, allowing the calculation of secret key rates, including finite key effects. This enables us to demonstrate, with a realistic single-photon source, positive secret key rates using our scheme over 227 km of optical fiber, equivalent to a loss tolerance one order of magnitude greater than nondecoy schemes. This Letter broadens the scope of single-photon sources in future quantum networks by enabling long-distance quantum key distribution with realistic levels of single-photon purity.

We have made measurements of the difference between the position angle (PA) on the sky and the polarization position angle (PPA) of radio sources using data from a combination of the Radio Fundamental Catalogue (RFC) across a range of frequencies between 2.7 and 15 GHz and Cosmic Lens All-Sky Survey (CLASS) which observes polarization at 8.4 GHz (X-band). For the 2111 sources with jet PAs measured in the X-band and a known redshift, the distribution is peaked at $\approx 0°$ as expected for no birefringence and it can be modeled by two populations: one which is a Gaussian with mean ${\mu }_{\beta }=(0.2\pm 1.0)°$ and standard deviation ${\sigma }_{\beta }=(14.7\pm 1.1)°$ and the other a uniform distribution of sources which are a fraction $f_{\beta }=0.72\pm 0.02$ of the total. Uncertainties in ${\mu }_{\beta }$ can be reduced to $\approx 0.6°$ by stacking measurements of the PA from other wavebands. We find that limits of $\approx 0.1°$ might be possible with a sample of $\sim {10}^5$ similarly selected sources and that this could provide a confirmation of recent claims of global birefringence made using the cosmic microwave background observations from the Planck satellite.

A search for $CP$ violation in the ${\overline{B}}^0\to {\overline{K}}^{*0}{\mu }^{+}{\mu }^{-}$ decay is performed using proton-proton collision data collected by the LHCb experiment during Run 1 and Run 2, corresponding to an integrated luminosity of $8.4{\mathrm{fb}}^{-1}$. The analysis exploits the full angular distribution of the decay, providing sensitivity to $CP$-violating effects in both vector and axial-vector contributions to this flavor-changing neutral-current process. The complex Wilson coefficients are determined within the weak effective theory through an unbinned maximum-likelihood fit to the angular observables, incorporating nonlocal hadronic amplitudes across the full dimuon mass spectrum. The precision of the $CP$-violation observables is improved by an order of magnitude relative to previous measurements, with the imaginary parts of the Wilson coefficients now determined more precisely than the real parts. No significant $CP$ violation is observed, and the results are consistent with the standard model.

A quantum quasicrystal was proposed to exist by mean-field, variational arguments in two-dimensional Rashba spin-orbit coupled BECs with dipolar interactions. Despite this remarkable prediction, there is little known about the superfluid character or stability of this quasicrystalline state against thermal and quantum fluctuations, whose importance is implied by the massive single-particle degeneracy of the Rashba Hamiltonian. Here, we apply field-theoretic numerical simulations based on a boson coherent state path integral representation to simulate the finite-temperature behavior of a periodic approximant of an octagonal quasicrystal. We find that the quasicrystal state maintains a 50% superfluid fraction down to low temperature, suggesting supersolid character. We compute a phase diagram that depicts a region of thermodynamic stability for the octagonal quasicrystal phase at low temperature. At intermediate temperature, the quasicrystal undergoes a first-order transition into a crystalline BEC with hexagonal symmetry. Our findings support a possible experimental realization of the octagonal quasicrystal in ${}^{164}\mathrm{Dy}$ quantum gases below a temperature of 75 nK.

Three-level systems exhibit quantum interference effects absent in two-level systems, making them important for quantum optics. Here, we study the coherent interaction of a $\mathrm{\Lambda }$-type three-level system with free electrons shaped by optical near fields. By treating the electron train as a quantum drive, we show that the interplay between electron modulation and the three-level system’s transition pathways induces tunable interference patterns. This interaction effectively realizes electron-mediated coherent population trapping. We identify a regime that enables complete population transfer between the two lower states and the preparation of a high-coherence superposition, manifested as dark states. In particular, these driven-dissipative steady states are independent of the initial state. Our Letter proposes shaped free electrons as a platform for steady-state coherent control of three-level systems, enabling atomic-scale state engineering.

Density-corrected density functional theory (DC-DFT) considers whether self-consistent densities yield optimal energetics in Kohn-Sham calculations. With considerable success in molecular calculations, we here apply DC-DFT to solid-state calculations with Hartree-Fock (HF) densities. We resolve a known anomaly: that dispersion corrections can worsen results as one climbs Jacob’s ladder. This is illustrated for simple covalent solids, such as Si. The relative energetics of phases of ice are also much improved with HF densities, as is CO adsorption on NaCl, while graphite interlayer binding is insensitive to its density.

Fractional excitations provide a key to identifying sought-after topological quantum spin liquid states in realistic materials. Their single-particle dynamics already presents a challenging many-body problem on account of the coupling to their emergent gauge field. Here, we study the spinon excitations of kagome ice, realized at the $2/3$ magnetization plateau of spin ice, by combining up-to-63-site exact diagonalization with an analytical state graph mapping. We find a macroscopically degenerate mode in the spinon spectrum. It originates from the destructive interference due to the interaction with surrounding gauge fields, a form of many-body caging. We explicitly construct, and count, the concomitant many-body wave functions. Finally, we discuss the possible role of these flat modes in the magnetization process of kagome antiferromagnets, in particular with regard to the asymmetric termination of the kagome ice magnetization plateau.

We consider interacting paraparticle chains with a constant $R$ matrix where the Hamiltonian sums over the internal degrees (flavors) of the paraparticles. For such flavor-blind Hamiltonians, we show a general factorization of the Hilbert space into occupation and flavor parts with the Hamiltonian acting nontrivially only on the former. For open boundaries, the spectrum therefore coincides with that of the occupation Hamiltonian $H_{\mathrm{occ}}$ with the flavor part merely adding degeneracies. For periodic boundaries, a cyclic reordering of the flavors leads to a separation of $H_{\mathrm{occ}}$ into flux sectors at fixed particle number, thus making the parastatistics directly observable in the energy spectrum. For important exemplary cases, $H_{\mathrm{occ}}$ reduces to the XXZ chain with flux, allowing for an exact solution. In the gapless regime, this solution shows flux-shifted $c=1$ conformal towers in the low-energy spectrum and a temperature-dependent chemical potential in the bulk thermodynamics.